Neal Ascherson: Every revolution has its rules. Ignore them and the fire will burn out

From Tahrir Square, television brings us two sorts of image. The close-ups of men mopping blood from their broken heads, cowled women shaking their fists at heaven, boys with dilated eyes shrieking that they will stay on the square until victory or death. And then the long shots, often from some high balcony, of the crowd itself.

Seen from above, this gigantic event resembles the surges of nature, rather than of human history. Sometimes the masses slowly pour forward and then halt in a dense, dark mass: the gravel and seaweed rushed up a beach by the storm and then dumped as the wave loses force. Sometimes you see thousands of separate human beings fleeing, wheeling, suddenly coming together and setting off in a new direction as if a collective mind had changed. Clouds of starlings, wild geese sensing danger.

It's no wonder that revolutionary crowds are given strange collective names, especially by those who fear them. It's as if the tens of thousands in Tahrir Square – or in Wenceslas Square, Prague, in 1989, or around the Bastille two centuries before – had fused into a single beast. And the individuals who form the crowd also like to feel they have been merged by rage and fire into a single Something, a being greater and nobler than the sum of its parts. "Wir sind das Volk!" they roared at the Stasi in Leipzig, 22 years ago. In Cairo, they say: "We are The People."

It's easier to define a revolutionary than a revolution. Hard-wired into most human beings, but never accessed by most of them, is the capacity to be transfigured, to be seized by confidence that a new world is being born. Everyone around is suddenly a brother or a sister. Looters may be carting off the Ministry's computers, but you are giving the Minister's bodyguard a white rose and he will break down in tears and rally to The People.

What persuades people to become The People, to "go down into the street" and risk everything? Hunger and unemployment, hatred of unfreedom, play their part. But the key safety-catch which must be knocked open is fear – or, more accurately, respect. In Tunisia and Egypt, hundreds of thousands have acknowledged their contempt for their rulers, and realised that they are no longer frightened of them. Lenin thought that revolution required not only that the masses lose patience but that the ruling class loses confidence in its own system. Tunisians and Egyptians picked up that whiff of uncertainty, and they marched.

All revolutions are different, but there are categories. Tunis was rather like Prague or Leipzig in 1989: a people loses fear and defies the security police; a regime inwardly rotten makes desperate concessions and then melts away. Cairo, on the other hand, begins to look ominously like Bucharest at the end of 1989. The dictatorship falters (and in Romania collapsed), but then chaotic bloodshed spreads over the city. Who is shooting at the revolutionaries? Which side is the army on? After weeks of lethal confusion, a compromise regime emerges, preserving many of the authoritarian instincts of the old tyranny.

The question for Tahrir Square has been the same since the protests began 10 days ago. How does a "victorious crowd" move on to become a revolution? The Cairo mass, for all its guts and resilience, doesn't seem capable of that move. The only recognisable structures to emerge are first-aid posts and food stalls. It has evolved no acknowledged leadership – there's no Egyptian Lech Walesa, no Vaclav Havel or Ayatollah Khomeini. Although vigilante groups are spread across the city, nobody has welded them together into a "revolutionary militia" to protect the movement.

There are reasons for these weaknesses. The main one is the crushing of Egyptian "civil society" by police terror during the 30 Mubarak years. A crowd needs more than coherent leadership. It requires institutional allies to achieve a revolution. It needs self-managing political parties, professional bodies, trade unions: allies who can crystallise demands and manage debates. But in Egypt such bodies, penetrated or castrated by the regime, have little independence. The great crowd, an astonishing mixture of angry plebs and young middle-class intellectuals, is on its own.

It's not that the square doesn't know what it wants. The common factor is to get rid of President Hosni Mubarak. Beyond that, political reform (the basic freedoms) and more vaguely formulated economic reform. The protesters are using the global language of human rights and liberties, in its American version. This makes them reluctant – so far – to "use violence", to charge forward and try to capture the centres of government at whatever cost in blood. Their enemies are not so reluctant.

The course for the Cairo insurrection now seems to be passive, rather than active. It will simply hang on in the square, enduring attack by government thugs and possibly the army, in the hope that its presence will eventually break the regime's nerve. In other words, the great protest has come to a halt. What else should it be doing? Nobody seems sure.

As well as a sympathetic civil society, a revolution needs rules. In any children's yard game, it has to be clear when you have touched base and won. Most crowds and their leaders make the rules up as they go along. But the French, in their long 19th-century series of failed or successful revolutions, worked out a rough sequence of boxes to be ticked.

First of all, the uprising in the street. Then the armed people had to capture the national assembly. Then, in the occupied chamber, the revolution would set up a "provisional government", proclaiming the end of the existing republic and the happy dawn of anther one. Next, the government would organise elections to a constituent assembly whose job was to draw up a new constitution. This would be put to a referendum. Finally, elections under the constitution for a new, permanent national assembly. Then, and only then, would the process of revolution be complete. Absurd? Dressing up a ravenous tiger in top hat and frock coat? Maybe, but sometimes it worked to give revolutions a sense of direction and even legitimacy. Rules help to avoid chaos. If the Egyptians agreed that capturing the parliament or the presidential offices marked victory, the people on Tahrir Square would know where to march.

In Ukraine in 2004, huge and apparently invincible crowds camped in the Majdan, Kiev's central square, until the fraudulent presidential election was cancelled and the way opened for the popular Viktor Yushchenko to take his rightful place. The demonstrators in Kiev, just like the men and women under siege in Cairo now, said that "the Orange Revolution" had transformed their lives, that their country would never return to the bad old days. Yet today Yushchenko's rival is back in power, and the country is still corrupt and repressive. In Ukraine, as in Romania, a leader was removed but much of the old system – lightly sanitised – survived. In both cases, the "victorious" crowds had no structure and developed no political instruments of their own.

If President Mubarak does fall in the next few days, what then? Does "The People" just go home, without leaving in place any political force to see that its other demands – freedom, plural democracy, the disbanding of the security apparatus – are carried through? The enormous collective animal on Tahrir Square has shown the world that it has lion-like courage, endurance and, self-restraint. But does it have imagination?

Neal Ascherson is a former foreign correspondent for The Independent on Sunday